FTP stands for File Transfer Protocol, it is a commonly used protocol for transferring copies of files over any network that supports the TCP/IP protocol (such as the Internet or an intranet).
There are two computers involved in an FTP transfer: a server and a client. The FTP server, running FTP server software, listens on the network for connection requests from other computers. The client computer, running FTP client software, initiates a connection to the server. Once connected, the client can do a number of file manipulation operations such as uploading files to the server, download files from the server, rename or delete files on the server and so on. Virtually every computer platform supports the FTP protocol. This allows any computer connected to a TCP/IP based network to manipulate files on another computer on that network regardless of which operating systems are involved (if the computers permit FTP access).
FTP was developed during the 1970s and 1980s to support file sharing on TCP/IP and older networks. The protocol follows the client-server model of communication. To transfer files with FTP, a user runs an FTP client program and initiates a connection to a remote computer running FTP server software. After the connection is established, the client can choose to send and/or receive copies of files. An FTP server listens on TCP port 21 for incoming connection requests from FTP clients. When a request is received, the server uses this port to control the connection and opens a separate port for transferring file data.
